In a wireless communication system, multi-user diversity is used for an independent time-variable channel environment between users. A variation in the channels of a plurality of users is monitored, and when it is determined by scheduling that the channel of each user is in the best condition, that is, the largest channel gain is obtained, resources are allocated to the users, thereby obtaining a diversity gain.
The diversity gain increases as a variation in a channel increases. Therefore, in a channel environment in which a variation in a channel is small or a channel varies slowly, there are restrictions on the diversity gain. A method of obtaining a diversity gain by rapidly changing the channel using a multiple transmission antenna in such an environment is called an opportunistic beam forming (hereinafter referred to as OBF) scheme. However, the OBF scheme has a problem in that it can obtain a sufficient multi-user diversity gain only when there are many users.
In addition to the OBF scheme, a method of obtaining a diversity gain by using multiple pilots to improve diversity in the selection of the pilot has been proposed. However, the method has a problem in that system capacity is lowered due to a large number of pilots.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.